Mining to mud: a multidisciplinary approach to understanding Victoria’s riverine landscape as a product of historical gold mining J. Grove1,2, J. Turnbull1, S. Lawrence1, P. Davies1, I. Rutherfurd2, E. Silvester3, F. Colombi3 and M. Macklin4 1Department of Archaeology and History, La Trobe University, Bundoora, VIC, Australian, jgrove@unimelb.edu.au 2School of Geography, University of Melbourne, Carlton, Australia 3Department of Ecology, Environment and Evolution, La Trobe University, Wodonga, Australia 4School of Geography & Lincoln Centre for Water and Planetary Health, College of Science, University of Lincoln, Lincoln, Lincolnshire, United Kingdom Introduction The Victorian gold rush began in 1851, resulting in massive demographic, land use, and social changes (Serle 1968). Rivers, during much of the gold mining history of Victoria, were used as a“free”resource, both to extract and process sediment. The effect on river systems around the state was catastrophic. A quarter of the length of the main streams was damaged. Even though the devastating environmental impact of Victorian gold mining was recognised at the time, it appears to have been forgotten today (Figure 1). This is despite extensive documentation of the number of mining operations, methods used, resultant environmental impacts and consequent legislation. The ARC discovery project“Rivers of gold”set up a multi-disciplinary team to try and reconstruct the historical development of mining across the state of Victoria, and to determine the legacy of this mining. One of the main consequences of gold mining was the production of alluvium that was known as“sludge”. ‘ Sludge’ shall mean water holding in suspension particles of mineral matter derived from mines or particles of debris or other waste matter derived from mineral or metallic ores or matrices whilst under treatment or particles of soil earth clay sand quartz rock gravel or other material delivered into the water in consequence of the operations of any mine, but shall not include water holding in suspension particles of soil only or of vegetable organic or other matter not connected with mining operations. (Shakespear, Walker, and Rowan 1887, xxviii) The sludge filled up channels and meant that stock couldn’t be watered, it also blanketed floodplains killing vegetation. Davies et al. (2018a), using a combination of approaches, estimate that around 650 million m3 of sediment was likely mined and input into river system from 1851–1900. The amount of gold won by miners decreased over this time period, and this decrease was accompanied by a decline in the numbers employed in the industry (Figure 2). These numbers bely the fact that in order to get payable amounts of gold more and more sediment needed to be mined, and that new technology had supplanted manpower. From 1851–58 20 million m3 of sediment was mobilised (2.5 million m3 a−1), whilst 492 million m3 were processed from 1859–1891 (15.4 million m3 a−1). The approach taken to understand the fate of the mined sediment, and whether there are any legacy impacts, is one that has combined the skills of archaeologists, historians, geochemists and geomorphologists. The evidence that these disciplines has provided is presented in eight different chronological stages. The project used state-wide data, where available, and more detailed data on three catchments: Ovens River, Loddon River and the Leigh-Yarrowee (Figure 3). The goal was to show what data can be collated across different research areas, and how it could be combined to provide multiple lines of evidence. Stage 1: Pre-European settlement (pre 1803) A baseline dataset needed to be created to understand the environment that miners modified. These data are not readily available across Victoria, and conditions were only reconstructed for the focus catchments. Evidence Whilst the pre-European vegetation across Victoria has been described using Ecological Vegetation Classifications, and Figure 1.  Mining at Guildford, near Castlemaine, during the gold rush (left), and the same scene in 2018 (right). Feature Mining to mud 44 PREVIEW JUNE 2019